Self-assembly of a [2]Pseudorotaxane Composed of Cucurbit[6]uril into Linear Pseudopolyrotaxanes by N–H···O, C–H···O and π···π Interactions

The [2]pseudorotaxane of cucurbit[6]uril (Q6) with 1,6-bis(imidazol-1-yl)hexane dihydrobromide was synthesized and its crystal structure was described. The structure of [2]pseudorotaxane was mainly stablized by host–guest C–H···O interactions. Self-assembly of the [2]pseudorotaxane produces infinite one-dimensional chains with intermolecular N–H···O, C–H···O, and π···π interactions; thus, a linear non-covalent pseudopolyrotaxane is formed.     

Electron-density studies on hydrogen bonding in chromone derivatives. Part II: comparative study

The experimental electron density of a chromone derivative was determined from a multipole refinement of 100 K X-ray synchrotron data and complemented by theoretical calculations with experimental and optimized geometry. Atomic and topological properties were obtained using the Quantum Theory of Atoms in Molecules approach. The examination of topological parameters unambiguously showed π-delocalization within the H-bonded ring. The application of source function analysis confirmed the intramolecular N–H···O hydrogen bond to be a resonance-assisted hydrogen bond. The topological study confirmed the covalent nature of N–H···O interaction and the electrostatic nature of weak C–H···O interactions.     

Synthesis,crystal structure and other properties of the complexes of Er(III), Yb(III) and Lu(III) with 4,4′-bipyridine and dichloroacetates

A novel mixed-ligand complexes of Er(III), Yb(III) and Lu(III) with title ligands were prepared and characterized by chemical and elemental analysis and IR spectroscopy, conductivity (in methanol, dimethyloformamide and dimethylsulphoxide). The thermal properties of complexes in the solid state were studied. The mode of metal–ligand coordination was discussed. The title compounds are isomorphic and isostructural in solid state. All atoms in studied compounds lie in general positions but occurrence of inversion on the midpoint of the bond linking two pyridine rings leads to existence in asymmetric unit one complex molecule and half of outer coordination sphere 4-bpy molecule. All chelating carboxylate groups are symmetrically bonded to the metal cations. The molecules of studied compounds are connected to the three dimensional network via O–H···O and O–H···N intermolecular hydrogen bonds. In the structures also exist C–H···O, C–H···Cl weak hydrogen bonds and π····π stacking interactions.     

Synthesis, structural characterization and thermal properties of three copper(II) complexes based on aryl hydrazide ligands

The thiosemicarbazide and hydrazide Cu(II) complexes, [Cu₃L₂¹(py)₄Cl₂] (1), [Cu(HL²)py] (2) and [Cu(HL³)py] (3), (H₂L¹ = 1-picolinoylthiosemicarbazide, H₃L² = N′-(2-hydroxybenzylidene)-3-hydroxy-2-naphthohydrazide, H₃L³ = 2-hydroxy-N′-((2-hydroxy-naphthalen-1-yl)methylene)benzohydrazide) have been prepared and characterized through physicochemical and spectroscopic methods as well as X-ray crystallography. Complex 1 has a centrosymmetric structure with –N–N– bridged Cu₃ skeleton. Neighboring molecules are linked into a 3D supermolecular framework by π–π stacking interactions, N–H···Cl and C–H···Cl hydrogen bonds. Complexes 2 and 3 have similar planar structures but different dimers formed by concomitant Cu···N and Cu···O interactions, respectively. Solvent accessible voids with a volume of 391 ?³ are included in the structure of complex 2, indicating that this complex is a potential host candidate. Thermogravimetric analysis shows that the three complexes are stable up to 100 °C.     

On the relationships between molecular conformations and intermolecular contacts toward crystal self-assembly of mono-, di-, tri-, and tetra-oxygenated xanthone derivatives

Oxygenated xanthones have been extensively investigated over the years, but there are few reports concerning their crystal structure. Our chemical investigations of Brazilian plants resulted in the isolation of four natural products named 1-hydroxyxanthone (I), 1-hydroxy-7-methoxyxanthone (II), 1,5-dihydroxy-3-methoxyxanthone (III), and 1,7-dihydroxy-3,8-dimethoxyxanthone (IV). The structures of these compounds were established on the basis of single crystal X-ray diffraction. The xanthone nucleus conformation is essentially planar with the substituents adopting the orientations less sterically hindered. In addition, classical intermolecular hydrogen bonds (O–H···O) present in III and IV give rise to infinite ribbons. However, the xanthone I does not present any intermolecular hydrogen bonds, meanwhile the xanthone II presents only a non-classical one (C–H···O). The crystal packing of all xanthone structures is also stabilized by π–π interactions. The fingerprint plots, derived from the Hirshfeld surfaces, exhibited significant features of each crystal structures.     

Syntheses,weak interactions, 3D network structures and magnetic properties of two salts based on bis(maleonitriledithiolate)copper(II) anion and substituted triphenylphosphonium cation

Two new salts, [BzTPP]₂[Cu(mnt)₂] (1) and [4NO₂BzTPP]₂[Cu(mnt)₂] (2) (BzTPP⁺ = benzyltriphenylphosphonium and mnt²⁻ = maleonitriledithiolate) have been prepared and characterized by elemental analyses, UV, IR, molar conductivity and single-crystal X-ray diffraction. The single-crystal structure analysis shows that 1 crystallizes in the monoclinic space group P2₁/n, while 2 crystallizes in the triclinic space group P−1. The effects of weak intramolecular interactions such as C–H···O, C–H···S, C–H···N, C–H···Cu hydrogen bonds and p···π, π···π stacking interactions in the solids generate a 3D network structure. It is noted that the change in the molecular topology of the counteraction when the 4-substituted group in the benzyl ring is changed from H to NO₂ results in differences in the crystal system, space group, weak interactions and the stacking mode of the cations and anions of 1 and 2. The magnetic susceptibilities of these salts measured in the temperature range 2.0 to 300 K show weak ferromagnetic coupling features with θ = 2.05 × 10⁻² K for 1 and 5.13 × 10⁻³ K for 2.     

DFT studies and AIM analysis of intramolecular N–H···O hydrogen bonds in 3-aminomethylene-2 methoxy-5,6-dimethyl-2-oxo-2,3-dihydro-2λ5-[1,2]oxaphosphinin-4-one and its derivatives

The intramolecular N–H···O hydrogen bonds in 3-aminomethylene-2 methoxy-5,6-dimethyl-2-oxo-2,3-dihydro-2λ⁵-[1,2]oxaphosphinin-4-one and its derivatives (F, H, Li, -BeH) were studied by DFT (density functional theory) methods. The results of calculations were obtained at B3LYP/6-311++G(d,p) level on model species, with the resonance-assisted hydrogen bonds (RAHB). Topological parameters such an electron density, its Laplacian, kinetic electron energy density, potential electron energy density, and total electron energy density at the bond critical points (BCP) of H···O/N–H contact bonds from Bader’s ‘Atoms in molecules’ (AIM) theory were analyzed in details. The energy of the N–H···O interactions studied here was found rather weak (E _HB = 2.53–12.08 kcal/mol). The results of AIM ellipticity indicated π-delocalization over all six atoms within ring.     

Four complexes with a bulky carboxylate ligand: syntheses,crystal structures,and luminescent properties

Abstract  

Four complexes of 3,3-diphenylpropanoate (L) and 4,4′-bipyridine as auxiliary bridging ligands were synthesized and characterized, namely [Zn(L)₂(4bpy)(EtOH)₂]_∞ (1), [Co(L)₂(4bpy)(EtOH)₂]_∞ (2), [Ni(L)₂(4bpy)(EtOH)₂]_∞ (3), and [Cu(L)₂(4bpy)(H₂O)]_∞ (4) (4bpy = 4,4′-bipyridine). X-ray single-crystal diffraction analyses show that complexes 1–4 all take one-dimensional (1D) fishbone-like structures incorporating bridging 4bpy ligands. The complexes show different supramolecular frameworks interlinked via intermolecular hydrogen bonds, π···π stacking, and/or C–H···π supramolecular interactions. Complex 3 only has a simple one-dimensional fishbone-like chain, whereas complexes 1 and 2 show two-dimensional supramolecular structures by interchain C–H···O hydrogen bonds. Complex 4 is assembled into two-dimensional layers and then an overall three-dimensional framework by a combination of interchain O–H···O hydrogen bonds and C–H···π supramolecular interactions. The luminescent properties of the ligands and their complexes were investigated.     

Syntheses, crystal structures, and properties of two salts based on Ni(mnt)2 (mnt2− = maleonitriledithiolate) anion and substituted triphenylphosphonium cation

Two new salts, [oClBzTPP]₂⁺[Ni(mnt)₂]²⁻(1) and [oClBzTPP]⁺[Ni(mnt)₂]⁻(2) ([oClBzTPP]⁺ = 1-(2′-chlorobenzyl)triphenylphosphonium and mnt²⁻ = maleonitriledithiolate) have been prepared and characterized by elemental analyses, UV, IR, MS spectra, single crystal X-ray diffraction, and magnetic susceptibility. The Ni ions of the Ni(mnt)₂ anions for 1 and 2 exhibit the square-planar coordination geometry. The Ni(III) ions of 2 form a 1D zigzag alternating magnetic chain within a Ni(mnt)₂⁻ column through Ni···S, S···S, or Ni···Ni interactions. The C–H···N, C–H···S, C–H···π hydrogen bonds or π···π stacking interactions play important roles in the molecular stabilizing and stacking of 1 and 2. Magnetic susceptibility measurements in the temperature range 1.8−300 K show that 2 exhibits diamagnetic behavior.     

Hydrogen-bonded supramolecular motifs in crystal structures of trimethoprim barbiturate monohydrate (I) and 2-amino-4,6-dimethylpyrimidinium barbiturate trihydrate (II)

In the present study, we report the crystal structures of two organic salts, namely 2,4-diamino-5-(3′,4′,5′-trimethoxybenzyl)pyrimidinium (TMP) barbiturate monohydrate (TMPBAR) (I), 2-amino-4,6-dimethylpyrimidinium (AMPY) barbiturate trihydrate (AMPYBAR) (II). In both complexes, one ring nitrogen of TMP and AMPY are protonated as a result of proton transfer from the−CH₂ group of barbituric acid. In compound (I), the TMP cation and barbiturate anion are paired through twoN−H···O and one N−H···N hydrogen bonds. This pair further self-organizes through N−H···O hydrogen bonds to generate an array of six hydrogen bonds. These arrays are further cross-linked by N−H···O hydrogen bonds forming a sheet-like structure. The water molecule is also embedded in the sheet via O−H···O and C−H···O hydrogen bonds, forming a rosette-like supramolecular motif. TMP cations are also bridged by alternating water molecules via C−H···O and O−H···N hydrogen bonds. In compound (II), the symmetrical barbiturate anions self-organize on both sides through N−H···O hydrogen bonds generating a supramolecular chain. These chains are cross-linked by the three water molecules. A pair of barbiturate anions and two water molecules constitute an array of four hydrogen bonds (DADA quadruple array). These arrays are cross-linked by another water molecule. 2-Amino-4,6-dimethylpyrimidine cations are paired through N−H···N hydrogen bonds. These pairs are bridged by three water molecules generating a supramolecular ribbon. The barbiturate chains and base pairs are arranged in an alternate manner via N−H···O and O−H···O hydrogen bonds to generate a 3-D network.     

Studies on mono- and dinuclear bisoxime copper complexes with different coordination geometries

Two new mono- and dinuclear Cu(II) complexes, namely [CuL¹]·0.5H₂O (1) and [(Cu₂(L²)₂)(DMF)]·0.5DMF (2) (H₂L¹ = 1,2-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)]methylene-aminooxy}ethane; H₂L² = 1,3-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)] methyleneaminooxy}propane), have been synthesized and characterized by X-ray crystallography. The unit cell of complex 1 contains two crystallographically independent but chemically identical [CuL¹] molecules and one crystalline water molecule, showing a slightly distorted square-planar coordination geometry and forming a wave-like pattern running along the a-axis via hydrogen bonding and π···π stacking interactions. Complex 2 has a dinuclear structure, comprising two Cu(II) atoms, two completely deprotonated phenolate bisoxime (L²)²⁻ moieties (in the form of enol), and both coordinated and hemi-crystalline DMF molecules. Complex 2 has square-planar and square-pyramidal geometries around the two copper centers, whose basic coordination planes are almost perpendicular and form an infinite three-dimensional supramolecular network structure involving intermolecular C–H···N, C–H···O, and C–H···π(Ph) hydrogen bonding and π···π stacking interactions of neighboring pyrazole rings.     

Self-assembled cobalt(II) Schiff base complex: synthesis, structure, and magnetic properties

Abstract  

A mononuclear complex [CoL₂Cl₂]·3.5H₂O (L = 2-[(2,2-diphenylethylimino)methyl]pyridine-1-oxide) has been synthesized and characterized by X-ray structure analysis. The crystal structure confirms the formation of an interesting porous framework with channel diameters of about 8 ? through weak C–H···π and C–H···Cl interactions. The magnetic properties of this complex have also been studied, and the susceptibility and magnetization data were analyzed in terms of the spin Hamiltonian formalism. They confirm substantial zero-field splitting, D/hc = 75 cm⁻¹.     

Cooperative N–H···N,N–H···O,and O–H···N bonded molecular dimers of two new 3,5-diaryl-1<Emphasis Type="Italic">H</Emphasis>-pyrazoles

Two new 3,5-diaryl-1H-pyrazoles: 3(5)-(4-tert-butylphenyl)-5(3)-(naphthalene-2-yl)-1H-pyrazole (1) and 5-(4-(benzyloxy)phenyl)-3-(furan-2-yl)-1H-pyrazole (2) were synthesized and characterized. Two strong ions peaks [2M]⁺ and [2M + Na]⁺ observed in the ESI–MS spectra are attributed to the dimerization process in solution formed by intermolecular N–H···N hydrogen bonds. The crystal structures have been determined by X-ray crystal structure analysis. Compound 1 exists as a pair of tautomers 1a and 1b, and its dimer [R ₂²(6) motif] is formed by the tautomers 1a and 1b. Compound 2 only exists as a 2a tautomer, and interesting intermolecular N–H···O and O–H···N hydrogen bonds link two pyrazoles and two methanol molecules, leading to the formation of an R ₄⁴(10) dimer motif.     

Different coordination modes and supramolecular aggregations in copper(II) pentane-2,4-dionato compounds with 2-pyridone and 3-hydroxypyridine

Abstract  

Copper(II) bis(pentane-2,4-dionato-κ² O,O′) compounds with 2-pyridone (1) and 3-hydroxypyridine (2) were prepared by the reaction of bis(pentane-2,4-dionato-κ² O,O′)copper(II) with selected ligands. The coordination of Cu(II) in both compounds is square pyramidal with the fifth coordination site occupied by the carbonyl oxygen atom of the 2-pyridone ligand in 1 and by the nitrogen atom of 3-hydroxypyridine in 2. The X-ray crystallographic studies revealed different crystal aggregation influenced by the ability of the 2-pyridone ligand to act as a hydrogen bond donor and acceptor, and 3-hydroxypyridine acting only as a hydrogen bond donor. Intermolecular N–H···O hydrogen bonding forms dimers in 1 and infinite chains in 2. Three-dimensional aggregation is achieved by π–π interactions and C–H···π (arene) hydrogen bonding.     

Unsymmetrical 1-naphthyltellurium(IV) dihalides: the interplay of Te···Br,C–H···Br and C–H···π interactions in the crystal structure of (1-naphthyl)(4-methylphenyl)tellurium(IV) dibromide

The crystal structure of (1-naphthyl)(4-methyl- phenyl)tellurium(IV) dibromide, the first unsymmetrical naphthyl containing diorganotellurium(IV) dibromide, shows the formation of one-dimensional supramolecular arrays where Te···Br secondary bonds link two parallel rows of molecules in a gear-teethed fashion. The weaker C–H···Br and C–H···π hydrogen bonds play important role in the formation of three-dimensional crystal lattice by cross linking these supramolecular motifs.     

Syntheses,molecular structures and magnetic properties of two hybrid organic–inorganic salts of bis(maleonitriledithiolato)copper(II) and substituted benzyl-4-dimethylaminopyridinium cations

Two new hybrid organic–inorganic salts, [BzDMAP]₂[Cu(mnt)₂](1) and [NO₂BzDMAP]₂[Cu(mnt)₂] (2) ([BzDMAP]⁺ = 1-benzyl-4′-dimethylaminopyridinium, [NO₂BzDMAP]⁺ = 1-(4′-nitrobenzyl)-4′-dimethylaminopyridinium, and mnt²⁻ = maleonitriledithiolate) have been characterized structurally and magnetically. The [BzDMAP]⁺ or [NO₂BzDMAP]⁺ cations (C) and the [Cu(mnt)₂]²⁻ anions (A) in 1 and 2 stack into a 1D alternating CC-A-CC-A-CC column. The Cu···N, π···π, C–H···N, C–H···O, and C–H···S weak interactions play important roles in the molecular stacking and generate a 2D or 3D structure of 1 and 2. The magnetic susceptibilities of these salts measured in the temperature range 2.0–300 K show weak antiferromagnetic coupling features with θ = −2.370 K for 1 and −0.222 K for 2.     

Two new lead(II) coordination polymer and discrete complex containing bipyridine ligands with different positioned methyl substituents: synthesis,characterization, crystal structure determination,and luminescent properties

Lead(II) coordination polymer [Pb(5,5′-dmbpy)(μ-NO₃)₂] _n (1) and mononuclear complex [Pb(6,6′-dmbpy)(NO₃)₂] (2) (where 5,5′-dmbpy is 5,5′-dimethyl-2,2′-bipyridine and 6,6′-dmbpy is 6,6′-dimethyl-2,2′-bipyridine) were synthesized from reaction of lead(II) nitrate with 5,5′-dmbpy and 6,6′-dmbpy, respectively. Both complexes were thoroughly characterized by elemental analysis, infrared, ¹H and ¹³C NMR, UV–Vis, emission spectroscopy, as well as single-crystal X-ray diffraction. Polymer 1 possesses one-dimensional (1D) chain structure, whilst complex 2 exhibits a discrete complex which provide an extended chain parallel to the [001] direction, via weak intermolecular C–H···O hydrogen bonding. Coordination number of Pb²⁺ in 1 and 2 are 8 and 6, respectively, with the stereochemically active lone pair, resulting in the hemidirected geometry for both complexes. The nitrate anions exhibit a tridentate chelating/bridging mode in 1, and a bi-chelating mode in 2. The supramolecular features in these complexes are guided/influenced by weak directional intermolecular C–H···O hydrogen bonding (1 and 2) together with π–π and C–H···π (1) interactions. The luminescence studies of 1 and 2 confirmed that the position of methyl substituent on 2,2′-bipyridine rings has a profound effect on the fluorescence emissions.     

A joint theoretical and experimental structural study of two novel 1,2,4-triazolo[3,4-<Emphasis Type="Italic">b</Emphasis>]-1,3,4-thiadiazine derivatives

In this study, two novel 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazine derivatives, 3-[2-(4-methoxyphenyl)ethyl]-6-phenyl-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazine (compound 1) and 3-[2-(3,4,5-trimethoxyphenyl)ethyl]-6-phenyl-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazine (compound 2), having analgesic–anti-inflammatory activity were synthesized and characterized by IR, ¹H-NMR, and mass spectroscopic techniques besides elementary analysis. Additionally, the structures and molecular packings of the mentioned compounds have been investigated by X-ray single crystal diffraction. The six-membered thiadiazine ring adopts the screw boat conformation in both the compounds. In the crystal packings of the compounds 1 and 2, C–H···N and C–H···O interactions link the molecules into a two-dimensional network and generate infinite chains. Furthermore, C–H···π intermolecular interactions provide further stability to the molecular packing in both the molecules. The conformers have been predicted by the potential energy surface scan employing the AM1 method. Geometry optimizations and electrostatic properties have been obtained using AM1 and ab initio quantum methods.     

Intramolecular S···O chalcogen bond in thioindirubin

Results of X-ray diffraction study and quantum-chemical calculations revealed that molecular conformation of thioindirubin molecule creates suitable conditions for formation of intramolecular C–H···O and S···O interactions. Analysis of molecular electrostatic potential (MEP) demonstrates existence of two areas of positive MEP (σ-holes) in the outermost part of the sulfur atom on the continuation of the lines of the C–S bonds. One of these σ-holes is oriented toward region of negative MEP around the oxygen atom of carbonyl group. Such situation corresponds to formation of σ-hole or chalcogen bond. Existence of both types of bonding interactions is confirmed by topological analysis of electron density distribution using “Atoms in Molecules” (AIM) theory. Energies of the C–H···O hydrogen bond and the S···O σ-hole bond derived from AIM and NBO theories are very close.     

A Self-Assembled 3D Hydrogen Bonded Network Constructed from Polyoxovanadate and Protonated Organic Substrate With a Solvent Hydrolysis Reaction

A self-assembled 3D hydrogen bonded network constructed from polyoxovanadate and organic substrate [V₁₀O₂₈][(CH₃)₂NH₂]₄(imidazolium)₂ (1) has been synthesized at room temperature and characterized by elemental analysis, IR and single-crystal X-ray diffraction. The structure of 1 can be regarded as being linked by the dimethylammonium cations of the decavanadate clusters to produce an interesting 3D network with a 4¹²6³ topology. In the resulting network, there exist one-dimensional channels along the a-axis, in which the imidazolium cations filled the channels. These imidazolium cations are involved in intermolecular hydrogen bonds of the types N–H···O and C–H···O, which seem to be main forces to stabilize the holistic structure.